FritzBox clear provider additive

Just to memorize myself how to clear a provider additive config on an old Fritz!Box (Before AVM decided to remove the telnet option)

cat /dev/null >/var/flash/provideradditive.tar
/bin/setfactorydefault
reboot

This will remove the provider additive config somebody applied to the box by an USB Stick with a ProviderAdditive=yes config.